1. Technical Field
The present invention relates to a tooth to be used in a jaw tooth model which allows students under dental training to experience oral works and therapeutic practices. More particularly, the present invention relates to a tooth to be used for experiencing morphological impartations in the formation of an anchor tooth, the formation of a cavity and so on, particularly a tooth to be used in a jaw tooth model provided with standards for evaluating tooth formation, a method of producing the same, and an apparatus for confirming tooth formation to be used in a jaw tooth model which is provided with standards for evaluating tooth formation.
2. Description of the Related Art
The use of a tooth for a jaw tooth model to be used for therapeutic practices in the oral cavity formed of an epoxy resin or a melamine resin is wide spread because of problems such as lack of natural teeth for therapeutic practices and infection diseases associated with a natural tooth.
However, a tooth for a jaw tooth model formed of an epoxy resin or a melamine resin exhibits cutting sensation which is different from that of a natural tooth. Therefore, even when performing formation trainings such as anchor tooth formation and cavity preparation, the cutting sensation and handling properties are different from that in actual oral work, which confuses the students. Specifically, the epoxy resin and the melamine resin are soft and thus there is a tendency to overcut them, while the natural tooth is hard and there is a tendency not to satisfactorily cut it. As a result, there is a possibility not to overcut it upon treatment and it is not easy to satisfactorily perform applications.
As a result of the need for a little harder material, a composite type tooth is commercially available. However even a composite type tooth has a cutting sensation of the tooth which is different from that of a natural tooth. Therefore, even when performing formation training such as anchor tooth formation and cavity preparation, the cutting sensation and handling properties are different from that in dental work in the oral cavity in practice, which confuses the students. To state the matter clearly, the cutting sensation includes a slipperiness and is substantially different from a natural tooth.
Japanese Unexamined Patent Publication (Kokai) No. 5-224591 discloses a tooth model which has cutting properties remarkably similar to the cutting properties of a natural tooth, and is suited for dental training of cutting works in a dental education. The tooth model contains, as main constituent components, an inorganic substance powder and a cross-linkable resin in a weight ratio within a range from 20%:80% to 70%:30%.
As the inorganic substance power constituting the tooth model, for example, alumina, zirconia, titania and silica are exemplified. It is not limited to the above compounds and various inorganic substance powders can be used.
However, since the cutting properties of the tooth model are different from those of a natural tooth, even when performing formation training such as anchor tooth formation and cavity preparation, the cutting sensation and handling properties are different from those of actual oral work which confuses the students. Also, only an inorganic substance powder is disclosed.
Japanese Unexamined Patent Publication (Kokai) No. 5-216395 introduces that there are provided a tooth model-which has cutting properties remarkably similar to the cutting properties of a natural tooth, and is suited for dental training of cutting work in a dental education and a method for producing the same. The tooth model contains, as main constituent components, a hydroxyapatite powder having a porosity of 40 to 80% and a (meth)acrylic acid ester-based resin in a weight ratio within a range of 20%:80% to 50%:50%.
A conventional tooth model has not satisfactory cutting properties. Therefore, the patent document discloses that the development of a tooth model having cutting properties resembling cutting properties of a natural tooth is required, but does not disclose sufficient cutting sensation.
Japanese Unexamined Patent Publication (Kokai) No. 5-224591 provides a tooth model which is most suitably used for therapeutic practice of periodontal diseases for dental students. The tooth model has such a configuration that at least the surface of a dental crown part has a Knoop hardness of 70 or more and at least the surface of a tooth root part has a Knoop hardness of 10 to 40.
The specification describes that “the tooth model may be formed of a material having any hardness, for example, metal, ceramics or resin from the viewpoint of a production method of a tooth model and economy, and also may include cavities”. However, the cutting sensation is not still improved.
Japanese Unexamined Patent Publication (Kokai) No. 5-241498, Japanese Unexamined Patent Publication (Kokai) No. 5-241499 and Japanese Unexamined Patent Publication (Kokai) No. 5-241500 describe an inorganic filler and a hydroxyapatite filler. However, any tooth model is formed of a resin as a base material, and the cutting sensation is not still improved.
Japanese Unexamined Patent Publication (Kokai) No. 2004-94049 describes an invention which provides a model tooth for dental training, that enables accurate shape measurement utilizing a laser beam.
The specification contains the disclosure that “As the material constituting the surface of a dental crown part of model tooth of the present invention, known materials can be used and examples thereof include porcelains such as ceramics; thermoplastic resin materials such as acryl, polystrene, polycarbonate, acrylonitrile-styrene-butadiene copolymer (ABS), polypropylene, polyethylene and poly ester; thermocurable resin materials such as melamine, urea, unsaturated polyester, phenol and epoxy; and materials obtained by adding, to these main raw materials, additives, for example, organic and inorganic various reinforced fibers such as glass fiber, carbon fiber, pulp and synthetic resin fibers, various fillers such as talc, silica, mica, calcium carbonate, barium sulfate and alumina, colorants such as pigments and dyes, or weathering agents and antistatic agents”. However, there is no description about preferred materials and the cutting sensation is not still improved.
The above patent document does not disclose a specific composition and only discloses a relation between the dental crown part and the tooth root part with respect to the cutting sensation.
Although the jaw tooth model has these problems, there have almost been no studies carried out on the problems of the jaw tooth model.
In the case of single molding of the epoxy resin and the melamine resin, when a cavity and an anchor tooth are formed, a university instructor generally teaches through visual observation whether or not the cavity and anchor tooth are satisfactorily formed.
Since this method takes humans as a standard, it is assumed that evaluation criteria slightly vary depending on the physical condition, environmental state upon measurement or the like. Furthermore, since only skilled persons can evaluate, considerable effort is required.
There is now reported a system in which 3D data of the tooth thus formed are obtained by PC, overlapped with the data of the formation by the teacher, and then evaluated.
However, according to this method, 3D data must be obtained for every formation and thus it was difficult to evaluate data of a number of students within a short time.
Some teeth comprising an enamel layer and a dentin layer each having a reproduced color are commercially available. However, these teeth could not be used for the method since they were not for evaluating the formation.
Japanese Unexamined Patent Publication (Kokai) No. 5-241498 describes that there is provided a tooth model suited for use, by dental students, in practice teachings for learning an endodontic treatment to cut the lesion part of a dentin texture and to remove the lesion of a marrow cavity part using a reamer or file so as to treat the lesion, such as dental caries, progressing down to the marrow cavity part.
There is introduced a tooth model which has the marrow cavity part comprising a pulp chamber part and a root canal part formed of a soft material having a Knoop hardness of 10 or less or formed as a cavity in a tusk-shaped member, and at least the dentin texture part surrounding the pulp chamber part is composed of a material containing hydroxyapatite and a (meth)acrylic acid ester-based resin as main components.
The tooth model of the above invention can only be used for treatment of lesion of the dental pulp part, and evaluation cannot be performed. Besides, it is impossible to evaluate treatment of formation of an anchor tooth, the formation of a cavity, and the like.
Japanese Unexamined Patent Publication (Kokai) No. 5-241499 and Japanese Unexamined Patent Publication (Kokai) No. 5-241500 provide a tooth model for dental crown repairing practices suited for use, by dental students, in dental training for learning a dental crown repairing treatment by cutting a tooth using a cutting bar, forming a cavity, performing an acid etching treatment and filling the cavity with a filling material. The enamel texture part of the surface of the dental crown part of a tooth-shaped member is composed of a hard material containing a dense inorganic substance powder, the dentin texture part inside the enamel texture part is composed of a softer material than the material of the enamel texture part, and also each material constituting the enamel texture part and the dentin texture part has an adhesive strength to a filling material to the surface of the part to be treated after an acid etching treatment of 50 kg/cm2 or more.
Although there is a possibility which specifically shows the shape of the natural tooth and enables experience of cutting closer to practice, it is impossible to evaluate a treatment of the formation of an anchor tooth, the formation of a cavity and the like.
Japanese Unexamined Patent Publication (Kokai) No. 2004-94049 introduces a model tooth for dental training, which has a dental crown part formed by imitating the shape of the tooth, wherein at least the dental crown part is formed of an opaque or translucent dental crown part forming material, and a light reflectance of the surface of the dental crown part is 70% or more to light having a wavelength of 700 nm. Since the shape of the dental crown part can be accurately measured by a non-contact high-speed three-dimensional shape analyzer, it is possible to accurately evaluate the results of various therapeutic practices and processing practices in the field of education utilizing such an effect.
However, since in the invention, the non-contact high-speed three-dimensional shape analyzer must be used for evaluation, large-scaled equipment is required and a long time is required for the measurement of the shape, and thus the model tooth could not be easily used for evaluation in a lesson.    [Patent Document 1] Japanese Unexamined Patent Publication (Kokai) No. 2004-94049    [Patent Document 2] Japanese Unexamined Patent Publication (Kokai) No. 5-241498    [Patent Document 3] Japanese Unexamined Patent Publication (Kokai) No. 5-241499    [Patent Document 4] Japanese Unexamined Patent Publication (Kokai) No. 5-241500    [Patent Document 5] Japanese Unexamined Patent Publication (Kokai) No. 5-224591    [Patent Document 6] Japanese Unexamined Patent Publication (Kokai) No. 5-216395    [Patent Document 7] Japanese Unexamined Patent Publication (Kokai) No. 5-224591